Rustproofing bath for iron and steel



Patented Feb. 9, 1926.

UNITED STATES JAMES H. GRAVELL, F ELKINS PARK, PENNSYLVANIA.

RUSTPROOFING BATH FOR IRON AND STEEL No Drawing. Application filed May 9, 1922, Serial No. 559,599. Renewed November 3, 1925.

To all whom it may concern:

Be it known that 1, JAMES H. GRAVELL, a citizen of the United States, residing at Elkins Park, in the county of Montgomery and State of Pennsylvania, have invented a new and useful Improvement in Rustproofing Baths for Iron and Steel, of which the following is a specification. 1

This invention relates to rust proofing iron and steel and the object of the invention is'to provide an improved bath compound for the purpose, whereby the rust proofing may be done more effectively and less care need be exercised in maintaining the bath in proper working condition.

According to the rust proofing process to which this invention is applicable, the articles to be rust proofed are immersed in a hot, weak solution of phosphoric acid and water until a substantial coating of-iron phosphate is formed and the time required varies, in practice, from one to several hours. s

This process is satisfactory where the surface of the articles is perfectly free from acids, for example, where the metal articles have been sand blasted, but where the work has been prepared for rust proofing by Pounds.

Phosphoric acid (85%) 100 Metallic sodium 4 The sodium dissolves forming monosodium phosphate in the acld.

The prepared acid thus formed is used pickling there is sufficient acid carried over- 'in the regular way in preparing the rust proofing bath.

The sodium in the solution changes the free sulphuric and other pickling and like acids into the sodium salts of these acids and these salts remain dissolved in the solution and do not precipitate to form a sludge at the bottom of the tanks. The ill effects of the foreign acids are destroyed without danger of causing a sludge to form on the work or to accumulate in the bottom of the tank.

My compound is used in the same way as unprepared phosphoric acid and meets all the requirements even when manganese dioxide or zinc phosphate or both are added to the bath which is often done in practice.

It will be evident to those skilled in the art that the metallic sodium may be replaced by chemical equivalents such as mon o-, di-, or tri-sodium phosphate without departing from the spirit of the invention,

-and the phosphoric acid may be made from material containing sodium so proportioned that the requisite amount of sodium will be present in the phosphoric acid when it is manufactured. My experience indicates that magnesium and potassium may be used instead of the sodium and it is understood that in the claims the term sodium includes also magnesium andpotassium, or

combinations of sodium, magnesium and potassium.

I claim:

1. A* bath for rust proofing comprising water, free phosphoric acid and monosodium phosphate which combining with pickling and foreign acids opposes the for-' maticn of a sludge.

2. The method of rust proofing a metallic surface which consists in forming a substantial coatingof iron phosphate on the surface by subjecting the surface to the action of a bath containing mono-sodium phosphate. free phosphoric acid and water, substantially as described.

JAMES H. GRAVE; i,

till 

